A scent is made up of traces of chemicals that evaporate off the body in what scientists call the "thermal plume". These chemicals can be left behind in sweat and other bodily fluids. The research team has found a way to collect samples that are as free of contamination as possible and analyse them using an "electronic nose" that breaks the scent down into its component chemicals.

In studies funded by the US Army Research Office, scientists found they could identify individuals by looking at the differing combinations of 44 chemical compounds secreted by the body.

They examined body odour samples of about 200 adults from Carinthia, a village in the Austrian Alps, chosen because no one from outside had settled there for many generations and the residents were mainly members of big families and genetically similar. Despite this, analysis showed each individual had a unique scent signature. "Scent allows us to learn about an individual's gender, their lifestyle, if they smoke, what they ate last night and whether they are stressed," Prof Brereton said.